1. Field of the Invention
The present invention relates to media protection systems, and more particularly, to a digital media/content protection system that provides the protection of the media owner's copyright during a media/content distribution process using cryptographic and watermarking techniques.
2. Discussion of the Related Art
In today's digital world, there is a great wealth of information that can be accessed in various forms: text, image, audio, and video. The relationships within the digital content triangle, “Owner, Distributor, and Customer” have become more and more complicated. The electronic representation and transfer of the digital media and content have increased the potential for any misuse and theft of such information and have significantly increased the problems associated with the enforcement of the copyright protection of such information.
These problems are rooted from the intrinsic features of the digital information: making copies of the information is easy and inexpensive, each copy is identical to the original (no quality loss), and the distribution of the copies is easy and fast. For these reasons, the authors and publishers of multimedia materials fear providing their works in the multimedia services and are seeking the solutions that can eliminate the problems associated with the copyright protection of the multimedia data. Thus, to preserve the digital media originality and to provide the security and copyright of the media, their distribution became a very important issue. There are two major techniques that are involved when providing a protection of the digital media: cryptography and digital watermarking.
Cryptography is a technology that is widely used for providing the data security. Relating to digital media, cryptography is used to provide the security of the access to copyright information access among the media managers in the Owner-Distributor-Consumer triangle. There are two main classes of cryptographic systems: symmetric key and public key (asymmetric key) encryption systems. A hybrid cryptographic system is a system in which both classes of systems are combined.
In a symmetric key encryption system, a single key can be used both to encrypt and decrypt. There are several efficient implementations of the symmetric key systems, but their key management is often troublesome.
In a public key encryption system, the processes of the data encryption and decryption are independent from each other. The data encryption process employs a public key, while the data decryption process requires a different (but mathematically related) private key. Knowing of the public key allows the encryption of a plaintext but does not allow the decryption of a ciphertext: the private key is necessary for the ciphertext decryption. A key owner keeps his private key secrete so that he is the only person who can decrypt a encrypted ciphertext and sign the digital data using his private key. If the key owner publishes his public key, then anyone can use that key to encrypt messages for the key owner and to verify the owner signature.
In a hybrid cryptographic system, a plaintext is encrypted with a symmetric algorithm having a symmetric key. The symmetric key itself is encrypted with a public-key algorithm having a public key. The encrypted symmetric key and data are then delivered to a recipient, who uses his private key to decrypt the symmetric key and uses the decrypted key to decrypt the data. This process is considerably faster than a public key encryption system, and it allows using a different symmetric key each time, considerably enhancing the security of the symmetric algorithm. Thus, the hybrid cryptographic system is ideal for transferring the protected media to a user.
Digital watermarking is a technology that is used for embedding copyright information data into various forms of media such as image, audio, and video with a minimum amount of perceivable degradation of the “host” signal. The embedded data should be invisible and inaudible to a human observer. The digital watermarking technology is often used to modify the played and recorded media signals and to keep track of a list of the involved playing or recording devices in order to detect any illegal copy maker. Using the technology, one can distinguish legal media from the illegal media copies. The purpose of embedding the copyright information into the digital media is to provide a proof of the copyright and assurance of the content integrity. Therefore, the embedded data should stay stable in a host signal even if the host signal is processed. Such a hidden and stable data, securely placed into a “host” signal to store the essential supplementary information, is called a watermark.
A watermarking process includes three basic stages: generating a watermark, embedding the watermark, and detecting the watermark. A watermark belongs to one owner who is the only person who can proceed to prove the ownership of the host signal.